454 Mag Valve guide confusion with machinist
07-10-2018, 05:05 PM
#1
454 Mag Valve guide confusion with machinist
Ok I took my head off my 454 mag because I had water leaking into the exhaust valve. I suspected it was the valve guide since its water cooled. Took it to the machine shop. He called me same day and said yep it was the valve guide but he had more in the shop and put in a new valve guide and still couldn't get it to seal and he didnt know what to do. Of course I dont know what to do so I started doing research and teh below information came from the repair manual. He took me my old valve measure at .617 at the top but .620 around the bottom. I asked him which way did he drive it out. He say towards the spring pad. According to below that should NOT be done since its technically the .616 and as I understand it stood the chance to crack the head. I went to the shop to understand the problem and found out he was using a valve guide that was stepped on both ends of the valve guide so I feel thats why it wouldnt seal at the bottom but would at the top. He is going to buy the valve guides that are only stepped on one end and try that. My question is a few things. Should the valve guide be put back in from the bottom? He says the travel distance is much shorter from the top thats why he puts it in from the top. Does he need to continue with a stepped valve guide measuring .616 at top and .620 at the bottom? Is the reason it isnt sealing because he used the wrong valve guide being stepped to .616 on the top and the bottom of the guide?
Lastly he told me as he was driving the valve guide out it the other piece drop out somewhere and he thought it might have went into the water jack somewhere but it wasnt a big deal. THIS is a big deal to me should I be worried? Is there procedure for finding or getting the other piece out?
===================
Exhaust Valve Guide Caution On
1965-98 GM Big Block Engines
These engines' valve guides were not intended as a replacement item from GM.
The guides were located into the head castings after the head was cast and
the exhaust guide is "water cooled".
The water-cooled guide also has two different size press fit diameters. Adding additional confusion to the matter, they also switched the location of the larger diameter sometime in 1985.
To determine which outside diameter guide you have and which direction to
remove an exhaust valve guide, the following procedure is suggested:
Drive the guide no more than .250" (6.35 mm) toward the valve spring side of
the head and stop. Then, measure the newly exposed area of the guide
OD next to the spring pad.
If the measurement is .620" it is the first style guide. To remove this
style guide, continue driving it toward the valve spring side of the head.
If the measurement is .616" , it is the second style guide. To remove
this style guide, you must drive it the opposite direction toward the combustion
chamber side of the head.
Lastly he told me as he was driving the valve guide out it the other piece drop out somewhere and he thought it might have went into the water jack somewhere but it wasnt a big deal. THIS is a big deal to me should I be worried? Is there procedure for finding or getting the other piece out?
===================
Exhaust Valve Guide Caution On
1965-98 GM Big Block Engines
These engines' valve guides were not intended as a replacement item from GM.
The guides were located into the head castings after the head was cast and
the exhaust guide is "water cooled".
The water-cooled guide also has two different size press fit diameters. Adding additional confusion to the matter, they also switched the location of the larger diameter sometime in 1985.
To determine which outside diameter guide you have and which direction to
remove an exhaust valve guide, the following procedure is suggested:
Drive the guide no more than .250" (6.35 mm) toward the valve spring side of
the head and stop. Then, measure the newly exposed area of the guide
OD next to the spring pad.
If the measurement is .620" it is the first style guide. To remove this
style guide, continue driving it toward the valve spring side of the head.
If the measurement is .616" , it is the second style guide. To remove
this style guide, you must drive it the opposite direction toward the combustion
chamber side of the head.
07-10-2018, 06:31 PM
#4
Well I get that but apparently 454 head were never meant to have the valve guides replaced. They used different sizes in different years and all 8 local machine shops said they would just have to look at it becasue they didnt know. Besides hes got some much time and work in the heads already I hate to say let me take it to someone else in be in the same boat....no pun intended.
07-10-2018, 06:53 PM
#5
07-10-2018, 07:31 PM
#7
Registered
My experience has been that once they start leaking the actual head casting is so corroded that replacing the guide doesn't do much good anyway. I thought someone used to make an oversize guide. Just looked in the SBI cat and dont see it there. I might take a look in the morning at the shop. If the head has a ton of work done to it and you really want to save it you could probably machine an oversize bronze guide. PEP might even have something.
07-10-2018, 07:57 PM
#8
My experience has been that once they start leaking the actual head casting is so corroded that replacing the guide doesn't do much good anyway. I thought someone used to make an oversize guide. Just looked in the SBI cat and dont see it there. I might take a look in the morning at the shop. If the head has a ton of work done to it and you really want to save it you could probably machine an oversize bronze guide. PEP might even have something.
07-10-2018, 08:07 PM
#9
Registered
It is #2 or 7 exhaust. It is not the guide. The heads are thin there and rot AROUND the guide. You fix it by scrapping it. The 454 block is pretty tough and can take 20 years if salt. The heads, not so much...
